How to adjust operator settings after leaving the settings panel
Unfortunately, you can't. Once you perform another operation, the changes are set.

However, the operator should retain its last-used settings; you can delete the knot and re-add it, then change the settings to suit your liking.

If you want to change the settings before doing anything else, you can use the panel in the Tool Shelf, or press F6 in the 3D View to bring up the options for the last-used operator.